1. Field of the Invention
The present invention is generally directed to dental guards worn by people to protect their teeth from the effects of grinding, and particularly, to an improved dental guard which is constructed of two layers; a soft layer, which contacts the user's teeth, bonded to a hard layer.
2. Description of the Prior Art
For many different reasons, some people grind their teeth, particularly during sleep. Depending upon the strength and frequency of the grinding, a person's teeth can be seriously damaged. To prevent the damage resulting from grinding, dental professionals often prescribe for their patients a dental protector, commonly referred to as a night guard, and also known as a stint. The dental guard acts as a protective barrier between the upper and lower sets of teeth, and is typically worn at night while the patient sleeps. Specifically, the dental guard covers the upper set of teeth, thus separating both sets of teeth.
There are two basic types of dental guards, referred to herein as a "hard guard" and a "soft guard." The hard guard is usually made from an acrylic. It is very inflexible and once formed cannot readily be altered. The soft guard is usually made out of a resin and is very flexible. A common resin used is a sheet resin mouth guard material sold by Healthco.
There are many types of problems associated with both of these guards. First, with respect to the hard guard, it usually is uncomfortable for most wearers because of its inflexible structure. In addition, it is very stressful to the teeth. Not only does the hard guard's structure create difficulty in wearing the device, but it also creates difficulties in removing it. It is not uncommon for persons with crowns to have them chipped by the hard guard. Also loose teeth may be pulled out by the guard. In addition, because of its inflexible structure, it often does not fit the mouth well, and therefore may bounce off the teeth and fall out of the user's mouth.
There are also problems associated with the soft guard. The soft guard tends to absorb bacteria and thus is difficult to clean. In addition, the soft guard blocks plaque into the teeth thereby causing related problems such as gingivitis or peridontal disease. In addition, it stains quickly and needs to be replaced often.
The hard guard and the soft guard are typically formed by two different processes. The first step in producing the hard guard is to create a model of the patient's teeth. This is accomplished by taking an alginate impression of the patient's upper and lower sets of teeth. This is a well known procedure in the art and need not be elaborated upon. The next step is to pour stone into the alginate impressions. The stone can be plaster, Coecal or any other material typically used in the dental industry. The stone is left to set and then a model of the patient's teeth is formed. The upper and lower models are then mounted or articulated using an articulator. The articulation process places the upper and lower models in the proper alignment to incorporate such characteristics as overbites, underbites and crossbites. Proper articulation is important because the night guard and the lower set of teeth must sit together properly when the patient closes his mouth. The model of the upper set of teeth is then taken to be waxed. Enough wax is placed on the model so that the correct vertical is achieved. The vertical is the distance the upper and lower sets of teeth should be separated. The upper model with the wax and the lower model are pressed together so that the lower model teeth make indentations in the wax.
The next step is to flask or invest the model of the upper set of teeth. A flask is a device well known in the art. A flask normally consists of four pieces: the base in which the model is placed; the knockout plate; the top half of the flask; and the lid. The model is placed in the base of the flask. Stone is then mixed and poured into the flask surrounding the model except for the wax portion which is not covered. Once the stone is set, the cast is lubricated with a lubricant such as Vaseline. The lubricant allows the bottom portion of the flask to be separated from the top portion when the top portion is later filled with stone. At that point the top portion of the flask is put in place and stone is poured over the model and the wax, filling the top half of the flask.
After the stone has set, the entire flask is then placed into a boiler. The boiling step causes the wax to melt away. The flask is opened and the lower half of the flask contains the model and the top half of the flask has a U-shaped imprint of the upper set of teeth. The model is then rinsed with a wax solvent to remove any excess wax not eliminated by the boiling process. Next a liquid separating media, such as modern foil, is placed on the model and the top half of the flask with the U-shaped imprint to prevent the acrylic from sticking to the model, or the top half of the flask, when it is placed on the model. A common acrylic used in dental applications is "Vitacrilic" manufactured by Fricke Dental Manufacturing Company. The acrylic is mixed and then left to set for a few minutes at room temperature until it becomes doughy. Once the acrylic is doughy, it can be manually applied to the model so that it completely covers the teeth of the model. A plastic sheet is placed on top of the acrylic to check if there is any porosity or impurities in the acrylic. The upper flask is joined with the lower flask.
The flask is then put under pressure which can range from about 1500-2500 p.s.i.g. The flask is opened and any excess acrylic is removed. The sheet is removed and then the upper half of the flask is again joined with the lower half and the entire flask assembly is put in a vise to exert a constant pressure. Next, the flask and vise are placed into a curing unit to cure for about nine (9) hours at about 165.degree. F. The flask is then opened with the model and acrylic mold bonded together in the lower half of the flask. In order to remove the acrylic mold, the model must be broken. The acrylic mold is then finished by removing the undercuts and polishing and buffing the entire mold thereby producing the hard guard.
The process to make the soft guard is somewhat different. Only one model is needed, that of the upper set of teeth, because articulation is not possible when making a soft guard. A model is made in exactly the same way as in the hard guard process discussed above. The model is then placed in a vacuum-set machine. A sheet of resin manufactured by Healthco is placed in the top of the vacuum-set machine. When the vacuum-set machine is turned on, the resin is heated so that it melts onto the model. Once the machine has completed its operation, the soft guard is basically formed. All that is thereafter required is a few finishing steps such as removing any excess material and cutting certain areas. Unlike the hard guard process, the soft guard process does not require that the model be broken to remove the guard. The soft guard can be removed easily and quickly because the material does not enter the inner ambrasia of the model. One of the problems with the process for making soft guards, however, is that bubbles may form in the guard due to the vacuum-setting process. Also the soft guard does not sit as well in the user's mouth as the hard guard because it is not articulated.
Accordingly, it is a primary object of the present invention to provide an improved dental guard that is comfortable to wear and less stressful to the user's teeth than conventional hard and soft guards.
Another object of the present invention is to provide a dental guard that can be easily altered to accommodate variations that may occur in the user's mouth without the necessity of producing an entirely new dental guard.
Further objects and advantages will become apparent from the following description and accompanying drawings.